Or, stated yet another way, we all suck at coordinating. It's a problem with our species. If something that requires self-sacrifice starts yielding value only after
everyone (or majority) does it, it simply doesn't happen, not spontaneously.
The history of human civilization - of governments, religions and movements, of gangs and corporations and worker unions - can be seen as attempts to surmount our inability to coordinate at scale. Laws, shared beliefs and ideologies, shunning, taboos, money - they're all tools for creating and maintaining coordination in large groups.
A classic essay on that topic: https://slatestarcodex.com/2014/07/30/meditations-on-moloch/.